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Research about Lake Tahoe

Source-linked reports with geographic coverage including Lake Tahoe.

29 records · Page 2Linked to original sources
USGS2009

Mercury flux to sediments of Lake Tahoe, California–Nevada

We report estimates of mercury (Hg) flux to the sediments of Lake Tahoe, California–Nevada: 2 and 15–20 µg/m 2 /year in preindustrial and modern sediments, respectively. These values result in a modern to preindustrial flux ratio of 7.5–10, which is similar to flux ratios recently reported for other alpine lakes in California, and greater than the value of 3 typically seen worldwide. We offer plausible hypotheses to explain the high flux ratios, including (1) proportionally less photoreduction and evasion of Hg with the onset of cultural eutrophication and (2) a combination of enhanced regional oxidation of gaseous elemental Hg and transport of the resulting reactive gaseous Hg to the surface with nightly downslope flows of air. If either of these mechanisms is correct, it could lead to local/regional solutions to lessen the impact of globally increasing anthropogenic emissions of Hg on Lake Tahoe and other alpine ecosystems.

California, Nevada↗
USGS2006

Back to the basics: Lake Tahoe, California /Nevada: Geography and mathematics

Back to the Basics: Lake Tahoe, California/Nevada* continues the Wetland Education Through Maps and Aerial Photography (WETMAAP) Program of exercises on teaching foundational map reading and spatial differentiation skills. It is the third published exercise from the Back to the Basics series developed by the WETMAAP Program. The current exercise modified is from the Lake Tahoe Back to the Basics workshop offered during the annual National Council for Geographic Education meeting. The focus of this exercise is on geography and mathematics, a unification of skills for spatial analysis and measurement.

California, Nevada↗
USGS2004

Gasoline-related organics in Lake Tahoe before and after prohibition of carbureted two-stroke engines

On June 1, 1999, carbureted two-stroke engines were banned on waters within the Lake Tahoe Basin of California and Nevada. The main gasoline components MTBE (methyl tert -butyl ether) and BTEX (benzene, toluene, ethylbenzene, and xylenes) were present at detectable concentrations in all samples taken from Lake Tahoe during 1997–98 prior to the ban. Samples taken from 1999 through 2001 after the ban contained between 10 and 60 percent of the pre-ban concentrations of these compounds, with MTBE exhibiting the most dramatic change (a 90 percent decrease). MTBE and BTEX concentrations in water samples from Lake Tahoe and Lower Echo Lake were related to the amount of boat use at the sampling sites. Polycyclic aromatic hydrocarbon (PAH) compounds are produced by high-temperature pyrolytic reactions. They were sampled using semipermeable membrane sampling devices in Lake Tahoe and nearby Donner Lake, where carbureted two-stroke engines are legal. PAHs were detected in all samples taken from Lake Tahoe and Donner Lake. The number of PAH compounds and their concentrations are related to boat use. The highest concentrations of PAH were detected in samples from two heavily used boating areas, Tahoe Keys Marina and Donner Lake boat ramp. Other sources of PAH, such as atmospheric deposition, wood smoke, tributary streams, and automobile exhaust do not contribute large amounts of PAH to Lake Tahoe. Similar numbers of PAH compounds and concentrations were found in Lake Tahoe before and after the ban of carbureted two-stroke engines.

California, Nevada↗
USGS2000

Morphology and processes in Lake Tahoe (California-Nevada)

Lake Tahoe was surveyed using a state-of-the-art, high-resolution, multibeam mapping system to provide an accurate base map for the myriad of ongoing environmental studies in and around the lake. The newly defined basin morphology shows steep basin margins on the northern, eastern, and western sides and a gentle margin on the southern side. Two large, flat plateaus several kilometers wide extend from the shore to about 40 m water depth in the northwestern sections of the basin. A series of ridges in the west and north are presumed traces of faults, some of which border the lake basin and some of which traverse across the northern section of the lake and converge in McKinney Bay. McKinney Bay is a large reentrant in the western margin that was created by a failure of the western margin that occurred about 300 ka. The failure generated a major debris avalanche that carried large blocks, some more than 1000 m long and 80 m high, accross the basin. Apparently, the debris avalanche was deflected by the eastern margin of the basin and flowed to the north and south. Small debris flows and slides have continued to occur in this area. Small debris aprons along the northern, western, and eastern margins, some apparently the remnants of collapsed terminal moraines formed in the basin from the 160 ka Tahoe Glaciation, which reached the edge of the basin. Eroded plateaus and ridges occur on a glacial outwash plain that covers the gentle southern margin. The plateaus and ridges are inferred to be remnants of another large terminal moraine of the Tahoe Glaciation.

California, Nevada↗
USGS1995

Evidence of autumn nitrogen limitation and contribution of picoplankton to carbon fixation in Lake Tahoe

Water samples were collected from Lake Tahoe at midlake and nearshore stations at three depths (25, 50, and 75 m, corresponding to light intensities of approximately 10, 1, and 0.1% of surface light) in May and September. The water samples were evaluated to decide the following: (1) whether carbon fixation was N-limited and whether there were differences between picoplankton and larger phytoplankters and (2) the relative importance of picoplankton carbon fixation and related photosynthetic parameters. Evidence of N-limitation was observed only in September at the midlake station for the populations at 50 and 75 m, and to a lesser extent at the nearshore station at 75 m, but only for the nanoplankton fraction. The contribution of picoplankton to total carbon fixation ranged from 34 to 69% and did not increase with depth. Low values for I k , the photoadaptation parameter, for deep water populations (0.1% light level) in September, but not May, suggested that these populations were adapted to low light in the fall but not the spring.

California, Nevada↗
USGS1981

Streamflow, sediment transport, and nutrient transport at Incline Village, Lake Tahoe, Nevada, 1970-73

The five principal creeks, First Creek, Second Creek, Wood Creek, Third Creek, and Incline Creek, with a cumulative drainage of 17.8 square miles, furnished a yearly average of about 15,000 acre-feet of runoff, mainly snowmelt, to Lake Tahoe during the 1970-73 water years. Annual runoff from the individual streams ranged from 460 to 7,070 acre-feet, and discharges ranged from 0.2 to 110 cubic feet per second. During the 4 years, the five streams delivered 31,000 tons of sediment, which averaged about 75 percent gravel and sand, 15 percent silt, and 10 percent clay, to the lake. Annual quantities ranged from 1,500 to 11,000 tons; individual streams furnished 20 to 5,200 tons annually. Measured sediment transport at the stream mouths ranged from 1 to 13,200 milligrams per liter and from 0.001 to 1,420 tons per day; sediment concentrations up to 63,200 milligrams per liter were measured at upstream tributary sites. Estimated annual sediment yields of principal drainage basins ranged from 3 to 930 tons per square mile from undeveloped areas and from 26 to 5,000 tons per square mile from developed areas; yields for developed areas appeared to average about 10 times those of undeveloped areas, and roadways apparently were the major source. Erosion disequilibrium caused by prestudy flash floods on two creeks continues to manifest itself through high natural sediment yields. The Second Creek flood of 1967 yielded about 75,000 tons in one afternoon. Fluvial nutrient transport seems quantitatively related to magnitudes of sediment and water transport. Movement rates of organic nitrogen and particulate phosphorus were greater than rates of other nutrient species moving to the lake.

Nevada↗
USGS1976

Sediment discharge from highway cut-slopes in the Lake Tahoe Basin, California, 1972-74

Streamflow and fluvial-sediment discharge data were collected at selected streams and highway gutters in the Lake Tahoe basin to determine the extent of erosion from highway cuts and to attempt to evaluate the effects of various land-treatment practices to reduce erosion. Estimate of long-term annual total-sediment discharge from six streams into the lake is 7,100 tons (6,400 tonnes), of which 2,300 tons (2,100 tonnes) is finer than 62 micrometres. During 1972-74, snowmelt runoff (April-July) accounted for 65 percent of the water and sediment discharge. Approximately 90 percent of the sediment is transported in suspension. Sediment measured at 16 gutterflow stations at the base of highway cut-slopes indicates that less than 100 tons (91 tonnes) of fine sediment per year are contributed to the lake from all California State highway cuts. Sediment-transport rates are highly variable, and an unknown part of the measured sediment was derived from sources other than highway cuts. Data were not adequate to demonstrate the effectiveness of treatments to stabilize cut-slopes.

Lake Tahoe↗
USGS1973

Sediment discharge in the Lake Tahoe basin, California, 1972 water year

Streamflow and fluvial-sediment discharge data are being collected at selected streams and highway gutters in the Lake Tahoe basin to determine the extent of erosion from highway cuts and to evaluate the effects of various land treatment practices to reduce erosion. Precipitation in the Lake Tahoe area during 1972 was 77 percent of normal; consequently, runoff was well below normal. Seventy-six percent of the total annual runoff during the 1972 water year occurred from March through June 1972. Sediment samples were collected during the year at streamflow gaging stations and at gutter stations at highway cuts to define the range of transport conditions. The major part (87 percent) of the annual suspended-sediment discharge during the 1972 water year occurred during the snowmelt runoff period, March through June.

California↗